Homoiostelea

fossil echinoderm class

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June 29, 2026

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The term "Homoiostelea" refers to an extinct class of echinoderms that existed from the Upper Cambrian to the Lower Devonian periods, approximately 400 to 510 million years ago. These marine invertebrates were characterized by a feeding arm and a complex stem composed of more than two series of plates. They are part of the subphylum Homalozoa, which are distinguished by their asymmetrical, flattened bodies and lack of five-part symmetry. The classification of echinoderms, including fossil groups like Homoiostelea, is complex and subject to ongoing research and debate among scientists.123

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echinoderm
Annotated classification
†Class Homoiostelea Upper Cambrian to Lower Devonian about 400,000,000–510,000,000 years ago; with a feeding arm and a complex stem composed in part of more than 2 series of plates. †Class Ctenocystoidea Middle Cambrian about 540,000,000 years ago; no feeding arm and no stem, but with unique…
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†Class Homoiostelea Upper Cambrian to Lower Devonian about 400,000,000–510,000,000 years ago; with a feeding arm and a complex stem composed in part of more than 2 series of plates. †Class Ctenocystoidea Middle Cambrian about 540,000,000 years ago; no feeding arm and no stem, but with unique…
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